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Low End knock 4.1 liter


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In my experience it seems that this problem reared its head only on the 4.1s FWD I have owned. For example I had an 85 FWD that had that issue. I just did what was suggested regarding the main bearing noise and added heavier oil and the car was fine. However, I had begun to hear a "slight" low end knock in my RWD 84 "only" when the engine warmed up and "only" in gear at idle. It never made any noises while driving just at idle when in gear at operating temp. Is this a common problem in both FWD and RWD 4.1s? To my knowledge I thought it was prevelant in the FWD because of the design of the serpentine belt and once you pulled back on the tensioner the noise would go away. On my RWD I have V belts.


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I don't think it matters. The belts are still putting upward pressure on the crank. The only difference is with the srepentine belt, you can easily remove belt tension to test it.

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While the V-belts would pull up on the crank, I would think the resultant load vector of all the V-belts would point in a slightly different direction than the FWD engines with the serpentine belt. It is a theory at this point as it has been years since I saw a RWD HT-4100 engine. I'd change the oil and use some 15W-40 Rotella oil instead of 10W30 and see if the problem goes away.

'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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